This core will serve as a centralized laboratory for the 1) propagation of Treponema pallidum strains for all projects; 2) for production of antisera directed against individual T. pallidum strains and recombinant msp- homologue molecules for Projects 1 and 2 for immunization of rabbits with recombinant msp-homologue molecules for protection studies in Project 3. T. pallidum cannot be propagated in vitro and must be continually passaged in rabbits, requiring specialized expertise, particularly for the non-Nichols strains, which are much more difficult to grow. These tasks are quite time- consuming and require a large amount of technologist effort, a swell as a large number of rabbits. The treponemes needed for the various experiments proposed in the three projects can be provided much more economically, in terms of minimizing the number of rabbits as well as technologist time, if they are propagated centrally. Provision of antisera raised by the core to the project leaders will also assure uniformity of specificity, permitting comparison of results from one project to another. The core will be directed by Dr. Sheila Lukehart, who has 25 years of experience in the propagation of pathogenic treponemes.